Touchscreen panels are typically incorporated in various electronic devices to detect a user input (i.e., user touch or hover) and to display content. The touchscreen panel includes an active portion capable of detecting the user touch/hover and displaying content. This active portion is typically formed from a display panel on top of which a capacitive sensing panel is provided which includes multiple layers of capacitive sensing circuitry arranged in a pattern.
FIG. 1 illustrates a capacitive sensing panel 100 utilizing a diamond-shaped pattern. The capacitive sensing panel 100 is of a type useful for a touchscreen panel for an electronic device such as a smart phone, GPS device, tablet computer, mobile media player, remote control device, or any other device capable of using a touchscreen panel. The sensing panel 100 includes an active portion 110 including a sensor pattern configured to assist in the detection of a user touch or hover (for example, through a finger or other body part as well as through a tool such as a stylus). The touchscreen panel 100 is formed from multiple ITO layers, namely, first ITO layer 112 and second ITO layer 114, disposed within the perimeter of the active portion 110. The first and second ITO layers 112 and 114 are separated by a dielectric layer 116. The first ITO layer 112 is patterned to include columns 115 of interconnected capacitive-sensing nodes 113, and a first layer of traces 115A coupled to each column of capacitive-sensing nodes 113 in the first ITO layer 112. The interconnected nodes 113 of any one column 115 are isolated from the interconnected nodes 113 of any adjacent column 115. The second ITO layer 114 is patterned to include rows 117 of interconnected capacitive-sensing nodes 113, and a second layer of traces 115B coupled to each row 117 of capacitive-sensing nodes 113 in the second ITO layer 114. The interconnected nodes 113 of any one row 117 are isolated from the interconnected nodes 113 of any adjacent row 117.
In the illustrated implementation, the interconnected nodes 113 have a diamond shape formed by a square rotated by forty-five degrees which allows for an interleaving of the row and column patterns to occupy a large surface area of the active portion 110. Thus, the space between four interconnected nodes 113 in two adjacent rows 117 is occupied by one node 113 of a given column. Conversely, the space between four interconnected nodes 113 in two adjacent columns 115 is occupied by one node 113 of a given row.
The first and second layers of traces 115A and 115B couple each respective row or column of capacitive-sensing nodes 113 to control circuitry 120. The control circuitry 120 may include drive and sense circuitry coupled to the traces 115A and/or 115B. For example, drive circuitry may be used to apply a signal to a trace 115A for a certain column and sense circuitry may be used to sense a signal on a trace 115B for a certain row. The opposite application of applying and sensing signals may, of course, also be provided using the control circuitry 120.
It is known in the art to operate the sensing panel in a number of distinct modes.
A first mode, referred to herein as a self-capacitance mode, configures the control circuitry 120 to sense the capacitance between any given column or row of interconnected nodes 113 and a surrounding panel reference (for example, ground). By sensing a change in self-capacitance for a given column or row of interconnected nodes 113, the control circuitry 120 may detect a user touch or hover at or near that given column or row of interconnected nodes 113.
A second mode, referred to herein as the mutual-capacitance mode, configures the control circuitry 120 to sense the capacitance at an intersection point between one column of interconnected nodes 113 and one row of interconnected nodes 113. By sensing a change in mutual-capacitance at a given intersection point between a column and row of interconnected nodes 113, the control circuitry 120 may detect a user touch or hover at or near that given intersection point.
It is further known in the art to provide a stylus 130 for use with the capacitive sensing panel 100. In a passive operating mode, the stylus 130 functions in a manner analogous to a user finger with respect to interacting with the capacitive sensing panel 100. In this regard, a change in capacitance (either self- or mutual-) is detected in response to the touch or hover of the stylus 130. In an active operating mode, however, the stylus 130 is configured to generate a signal 132 which can modify the charge on the nodes 113 of the capacitive sensing panel by means of capacitive coupling. If the stylus signal 132 is modulated by information (data), then the charge of the nodes 113 will likewise be modulated in accordance with that information and the modulated change in charge at the nodes can be detected (sensed) by the control circuitry 120 to recover the information sent by the stylus 130 in the signal 132.
The control circuitry 120 can be configured to drive a signal on the interconnected nodes 113 of the columns 115 and/or rows 117 of the capacitive sensing panel to place a charge on the nodes 113 which is capacitively coupled to the stylus. If the control circuitry signal is modulated by information (data), then the charge of the nodes 113 will likewise be modulated in accordance with that information and the modulated change in charge at the nodes can be detected (sensed) by the active stylus 130 to recover the information sent by the control circuitry 120.
It is thus possible for the control circuitry 120 and active stylus 130 to engage in a bidirectional communication. Establishing a protocol governing such a bidirectional communication is critical to supporting a cooperative relationship between the control circuitry and the active stylus 130. It is also important that the protocol support operation of the capacitive sensing panel 100 in non-stylus operations, such as detecting a user finger or hover, in a manner that is perhaps simultaneous with active stylus communication. It is further important that the protocol support operation of the capacitive sensing panel 100 with respect to communicating with a plurality of active styluses.